The substance has come under more scrutiny after it was discovered in the toxicology tests of two soldiers who suffered heart attacks and died during physical training at a military base in the southwestern United States.

Gordey said he tries to steer young athletes, including basketball player James Thornton, 18, in the right direction.

"I'm not going to be a pro player, but my chances, I don't want to ruin them or hurt my body in the long term when I get older," Thornton said.

The federal warning and military investigation come nearly six years after DMAA hit the market in the United States. Major League Baseball and the World Anti-Doping Agency have banned the substance as a performance-enhancing drug.